US stocks were almost perfectly flat last week, despite some signs that the longest period of calm in decades is about to be broken.

The nervous climb higher could continue this week, if earnings reports from health insurers, utilities and others keep the second-quarter growth streak going.

The earnings season was going according to the script of "better-than-expected" until Thursday morning. According to Thomson Reuters data providers, about three-quarters of companies in the Standard & Poor's 500 have reported earnings ahead of Wall Street targets, with only 200 left to go. Among the high-profile earnings "beats" were telecom giants AT&T and Verizon Communications, both of which grew profits despite intense competition and were duly rewarded with stock rallies.